Contact lens manufacturing involves multiple complex operations. Each of these operations requires a high degree of accuracy in order to achieve a precise fabrication for the contact lens.
An unprocessed contact lens is generally known as “button.” The button must be precisely aligned to a block, and then fixed to the block using a fixing material such as wax, glue, or other adhesive, so that subsequent machining or other operations on the button can be conveniently performed. This process of fixing a button to a block is referred to as “blocking.” A device that performs the blocking must accurately align the button with the block in order to achieve certain optical characteristics of the lens. Precise alignment and positioning of button during blocking reduces prism, increases concentricity of the lens and permits control of the center thickness of the lens.
In conventional systems, a button is typically transferred to a block in such a way that an axis of the button is more or less aligned to an axis of the block. The block is then moved a known distance relative to the button (or vice versa) so as to contact with the button and fix the two together with the adhesive. This process presents problems if the thickness or geometry of the button varies. If the button is too thick, the block may deform the button. If the button is too thin, the block may not achieve sufficient “contact” to achieve proper adherence. In order to compensate these variations, manual adjustments to this distance may be required. These adjustments are time consuming and require a skilled operator.
Furthermore, conventional systems typically dip the block in the fixing material or dispense the fixing material through a nozzle. One problem with these methods is a non-uniform adherence of the wax on the block. In addition, wax left in the nozzle cools, causing it to solidify, particularly at the tip, thereby hampering further wax from being dispensed.
Other drawbacks also exist.